New convenience constructors and other minor changes

- error builder convenience constructors
- recovery attempters convenience constructors
- changing alert recovery attempter delegate method as in issue #8
- documenting some methods
- adding new keys to AppTranslator project file
- podspec like CocoaPods/Specs@b9359ef2a7fdd4edc5d7e952073bcaea4d49412a
Revert "New convenience constructors and other minor changes"

This reverts commit 3c4944b2432fb5cf401a1cd23b9e1bb4793de3d1.
Adding error builder convenience constructor

- creating category
- adding new keys to AppTranslator project file
Adding recovery attempters convenience constructors

- adding block recovery attempter convenience constructor
- adding alert recovery attempter convenience constructor
- changing alert recovery attempter delegate method as in issue #8
- removing mr_didRecovery
Several fixes for builders created with errors

- adding facebook keys to builder's userInfo
- avoiding to add keys not present in the error's userInfo
- changing underlying exception pattern to strong
Podspec like CocoaPods/Specs@b9359ef
New imports

- adding MRErrorBuilder+NSException.h
- adding ErrorKitDefines.h to example's pch
Documenting some methods
Improving imports in some files

- fixing category name
- adding conditional import to AVFoundation/AVTime.h
- fixing extension import